The present invention relates to an automotive electric power supply.
The electrical energy needed in vehicles for powering the various electrical consumers is taken from a rechargeable battery which is charged by an alternator from operation of the internal combustion engine. One of the battery terminals is directly connected to vehicle ground, the other battery terminal, generally the positive terminal, is fed to various consumers via a distributor including several outputs and integrated fuses.
The invention provides an automotive electric power supply which is smart in optimizing the energy reserve made available by the rechargeable battery according to the demands. In accordance with the invention, between the input for one battery terminal and at least one of the outputs of the distributor, a semiconductor switch is connected which is driven by an electronic controller; the controller has an input interface for sensor signals representing operating parameters. The controller is thus active in controlling the consumer(s) connected to the output provided with a semiconductor switch. This control may involve power ON/OFF as required or also modulation, more particularly pulse width modulation.
In one particularly advantageous embodiment of the invention at least the one output connected to the vehicle lighting formed substantially by incandescent bulbs is regulated by pulse width modulation to a voltage value as defined effective for the incandescent bulbs. Now, the charging voltage supplied by the alternator for the rechargeable battery no longer needs to be limited to a value, taking into account the life of the incandescent bulbs, which is sigificantly lower than the optimum charging voltage under certain operating conditions.
It is further provided for in the preferred embodiment to generate a parameter representing the charge condition of the rechargeable battery by permanently monitoring the charging/discharging currents and integrating the current values as sensed. Depending on the charge condition of the battery the various consumers can then be supplied from the rechargeable battery according to a priority scheme. This concept enables essential functions to be maintained over an extended time period when the battery is low so that the vehicle can remain operative longer, for example, when the alternator is down.